Method for forming a film

ABSTRACT

A method for forming a film by a plasma CVD process in which a high density plasma is generated in the presence of a magnetic field is described, characterized by that the electric power for generating the plasma has a pulsed waveform. The electric power typically is supplied by microwave, and the pulsed wave may be a complex wave having a two-step peak, or may be a complex wave obtained by complexing a pulsed wave with a stationary continuous wave of an electromagnetic wave having the same or different wavelength as that of the pulsed wave. The process enables deposition of a uniform film having an excellent adhesion to the-substrate, at a reduced power consumption.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for forming a film.

[0003] 2. Description of the Prior Art

[0004] Films have been heretofore deposited by various processes such asCVD (chemical vapor deposition), sputtering, MBE (molecular beamepitaxy), and the like. In plasma enhanced CVD (referred to simplyhereinafter as plasma CVD), the use of high frequency excitation,microwave excitation, hybrid resonance and the like has been developed.Particularly in the plasma CVD process which utilizes a resonance with amagnetic field (referred to as “plasma CVD in magnetic field”,hereinafter), the development thereof has actively taken place and,because of its high film deposition efficiency which results from theuse of a high density plasma, its diversification in application hasbeen expected. In the practical film deposition in the presence of amagnetic field, however, a difficulty has been encountered to deposituniform films on an irregular surface without being influenced by suchsurface irregularity. This difficulty has hindered practical progress ofthe microwave CVD in magnetic field in the industries. The fact that aplasma CVD in magnetic field consumes an enormous amount of energy atits operation also is a bar to its gaining popularity in the industrialfield. A diamond-like carbon (DLC) film can be uniformly deposited on asubstrate as large as 10 cm or more in diameter by the use of microwaveplasma CVD in magnetic field. In the deposition of such DLC films bythis process, the diamond nuclei formed in the vapor phase are trappedon the substrate upon their contact with the substrate. Thus, the DLCfilm grows spread in a tapered form from each nucleus, and results in afilm having poor adhesion with the substrate. Furthermore, since thediamond crystals grow in a tapered form from a diamond nucleus centertrapped on the substrate, a compression stress accumulates around thegrain boundaries within the DLC film. The poor adhesion of the film withthe substrate and the compression stress within the film haveconstituted a hindrance to the practical use of DLC films.

SUMMARY OF THE INVENTION

[0005] An object of the present invention is to provide a process ofdepositing uniform films.

[0006] Another object of the present invention is to provide a processof depositing films with small power consumption.

[0007] Still another object of the present invention is to provide aprocess of depositing films which have excellent adhesion withsubstrates.

[0008] The foregoing objects and other objects have been achieved bydepositing films by a plasma CVD process which takes advantage of theinteraction between a magnetic field and an electric field, e.g. a highfrequency electric field, induced by supplying an electric energyintermittently, or of that between a magnetic field and an electricfield, e.g. a high frequency electric field, induced by supplyingthereto an electric energy intermittently and a stationaryelectromagnetic energy continuously which are superposed upon eachother. The magnetic field may be generated by supplying an electricenergy intermittently. Alternatively, the magnetic field may be obtainedby supplying either a DC current or a pulsed current to a Helmholtzcoil. Furthermore, rise and decay of the pulsed current for generatingthe magnetic field intermittently and those of the electric power forgenerating the electric field intermittently may be synchronized witheach other. In a typical embodiment, a microwave electric energy issupplied to generate the high frequency electric field.

[0009] In FIGS. 3(A), 3(B), and 3(C) are given examples of time versuspower (effective value of power). FIG. 3(A) shows a shape having twodifferent peak values. Such a power is particularly effective inincreasing production of substances over a certain threshold value whilesuppressing the production of substances having an energy of productionlower than the threshold value. FIG. 3(B) shows time versus power(effective value of power) of a wave obtained by superposing a highfrequency electric wave supplied intermittently upon a low powerelectromagnetic stationary wave supplied continuously, wherein theinitial waves have the same frequency. FIG. 3(C) also shows time versuspower (effective value of power)of a wave obtained by superposing a highfrequency electric wave supplied intermittently upon a low powerelectromagnetic stationary wave supplied continuously, however, thefrequency of the initial waves are differed. The plasma CVD of thepresent invention is referred also to as a pulsed plasma CVD hereinaftersince the power has a pulse shape as shown in FIGS. 3(A) to 3(C). Theuse of waves obtained by the superposition enables rapid deposition ofthe films, and is useful when a stable plasma cannot be obtained only byan intermittently supplied wave due to the structural allowance of theapparatus or to the conditions restricting the film deposition process.Thus, from the characteristic of a pulsed plasma CVD which enables auniform formation of nuclei for film growth on the surface ofsubstrates, the process enables deposition of a highly homogeneous filmon an article having an irregular surface on one hand; on the otherhand, from the fact that a high electric power can be concentrated at apulse peak as compared with a stationary continuous power, the filmdeposition can be carried out at an increased efficiency.

[0010] To obtain a film of uniform thickness extended over a large areaon a substrate, the film deposition is conducted in an apparatus theinner pressure of which is elevated to a range of from 0.03 to 30 Torr,preferably, from 0.3 to 3 Torr, using a high density plasma takingadvantage of hybridized resonance. Since the pressure is maintainedhigh, the mean free path of the reactive gas is shortened to a range offrom 0.05 mm to several millimeters, particularly to 1 mm or less. Thisfacilitates dispersion of the reactive gas to various directions, whichis advantageous for depositing films on the sides of the articles havingirregular surfaces. Thus, the *rate of film growth is, accelerated.

[0011] The article to be coated with a film is placed either in ahybridized resonance environment or in an activated environment remotefrom the hybridized resonance environment, to thereby coat the surfacethereof with the reaction product. To achieve efficient coating, thearticle is located in the region at which a maximum electric fieldintensity of the microwave power can be obtained, or in the vicinitythereof. Furthermore, to generate and maintain a high density plasma ata pressure as high as in the range of from 0.03 to 30 Torr, an ECR(electron cyclotron resonance) should be generated in a columnar spaceunder a low vacuum of 1×10⁻⁴ to 1×10⁻⁵ Torr and a gas, a liquid, or asolid is then introduced into the columnar space to produce a plasma,which is then maintained under a high pressure in the range of from 0.03to 30 Torr, preferably from 0.3 to 30 Torr, so as to obtain a spacehaving a highly concentrated product gas, said concentration per volumebeing about 10² to 10⁴ times as large as the gas concentration normallyused in a conventional ECR CVD process. By thus realizing the particularenvironment, the film deposition of a material which undergoesdecomposition or reaction only at such a high pressure becomes possible.The particular films which can be obtained include carbon films, diamondfilms, i-carbon (carbon films containing diamonds or microcrystalgrains), DLC (diamond-like carbon films), and insulating ceramics, andmetallic films, in particular films of metal having high melting point.

[0012] In summary, the process according to the present inventionutilizes plasma grow discharge and comprises a known microwave plasmaCVD process to which a magnetic field is added to utilize theinteraction of the magnetic field with the high frequency (micro wave)electric field. However, the ECR conditions are omitted from theprocess. The process according to the present invention conducts thefilm deposition in a hybridized resonance space using a high densityplasma having a high energy, under a high pressure in the range of from0.03 to 30 Torr. In the process according to the present invention, theplasma excitation is carried out with a pulsed wave or a combination ofa pulsed wave and a stationary continuous wave, as set forth above,under a high energy state in the hybridized resonance space to therebygenerate active species at an increased amount and also to effecthomogeneous nuclei formation on the surface of the substrate. Thisenables the formation of a thin film material at an excellentreproducibility.

[0013] The power is supplied in pulses, as mentioned earlier, at anaverage power of from 1.5 to 30 KW with a peak pulse about three timesthe average power. The primary pulse should be supplied at a period offrom 1 to 30 ms, preferably from 5 to 8 ms. Since the intensity of themagnetic field can be varied as desired, it is another characteristic ofthe process according to the present invention that the resonancecondition can be set for not only the electrons but also for a specifiedion.

[0014] In the deposition of a DLC film, for example, a pulsed wavehaving relationship between time and power (effective value of power) asshown in FIG. 4 can be applied. Preferably, the bonding within the DLCfilm is in sp³ hybridization. The ratio of the dissociation energy forsp³ hybridization to that for sp² hybridization is 6:5. In FIG. 4, itcan be seen that the first peak 30 is 6/5 times as high as the secondpeak 31. In this case, the energy for the first peak 30 is preferablysmaller than the dissociation energy of sp³ hybridization but maintainedhigher than the dissociation energy of sp² hybridization, so as not tobreak the sp³ hybridization bonding but to promote breakage of sp²hybridization bonding. More specifically, for example, the energy of thefirst peak is set in the range of from 5 to 50 KW, and that of thesecond peak is set in the range of from 4.1 to 46 KW. Furthermore, in apulsed high frequency plasma CVD, the nucleus formation is activatedwhile the growth of the formed nuclei is suppressed. Such a phenomenaresults in a uniform formation of crystal nuclei over the substrate,which is followed by a growth into a DLC film composed of columnarcrystals, said crystals being substantially one-direction orientedtoward the upper direction. Thus, a DLC film having a uniform crystalstructure and dominant in sp³ hybridization can be deposited at a highreproducibility, free from problems frequently encountered inconventional processes, such as the stress due to tapered film growthand the peeling off of the deposited film induced therefrom. The pulsedwave power may be acicular pulse power, as well as the powers shown inFIGS. 6(A) and 6(B).

[0015] In another embodiment according to the present invention, a light(such as an ultraviolet (UV) light) may be simultaneously irradiated tothe activated species to maintain the activated state for a longerduration. That is, the process comprises irradiating a light (e.g., a UVlight) simultaneously with the generation of a high density plasma bythe interaction of the pulsed microwave and the magnetic field, so thatatoms excited to a high energy state can survive even at locations 10 to50 cm distant from the area at which the maximum electric fieldintensity of the microwave power is obtained, i.e., the area at which ahigh density plasma is generated, since the high energy state issufficiently maintained even on the surface of the article. This processenables deposition of a thin film over a further larger area. In theembodiment according to the present invention, a cylindrical column wasestablished in such a space, and the article on which the film is to bedeposited was provided inside the column to effect film deposition.

[0016] The generation of the microwave (at an average power in the rangeof from 1.5 to 30 KW) may be synchronized with the generation of themagnetic field using an electric power the pulse form of which is shownin FIG. 6(A). Alternatively, a multistep rectangular pulsed electricpower as shown in FIG. 6(B) or that as shown in FIG. 6(C) may be used inplace of the pulsed electric power illustrated in FIG. 6(A). A multisteprectangular pulsed wave may be applied, for example, in the depositionof a DLC film. Since the microwave and the magnetic field in thisinstance can be supplied with a peak power of about 5.0 to 50 KW if sucha pulsed wave is used, the result is about 30 to 40% increasedefficiency as compared with the case a plasma CVD apparatus is operatedin a magnetic field with an input of an ordinary continuous wave at apower of from 1.5 to 30 KW. This enables reduction of power consumptionof the plasma CVD apparatus operated in the presence of a magneticfield. The pulse duration of the pulsed wave should be in the range offrom 1 to 10 ms, more preferably, from 3 to 6 ms.

[0017] It is also clarified that a film composed of more densifiedcrystal grains can be uniformly deposited on the article irrespective ofthe surface irregularities of the article by applying a pulsed wave to aplasma CVD process in a magnetic field. This is also an advantage of theprocess according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a schematic of an apparatus for microwave CVD inmagnetic field according to the present invention;

[0019]FIG. 2(A) shows a magnetic field obtained as a result of acomputer simulation;

[0020]FIG. 2(B) shows an electric field obtained as a result of acomputer simulation;

[0021] FIGS. 3(A), 3(B), and 3(C) each show a pulsed waveform accordingto the present invention;

[0022]FIG. 4 shows a pulsed waveform according to the present invention;

[0023]FIG. 5 is a schematically shown cross sectional view of a DLC filmaccording to the present invention; and

[0024] FIGS. 6(A) to 6(C) each show a pulsed waveform according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1

[0025] Referring first to FIG. 1, a microwave plasma CVD apparatusaccording to the present invention, to which a magnetic field isapplicable is shown. The apparatus comprises a plasma generating space1, a supplementary space 2, Helmholtz coils 5 and 5′ for generating themagnetic field, a power source 25 to supply energy to the Helmholtzcoils, a generator 4 for generating pulsed microwaves (also forgenerating waves obtained by superposing a pulsed wave upon a stationarycontinuous wave), a turbo molecular pump 8 which constitutes anevacuation system, a rotary pump 14, a pressure control valve 11, asubstrate holder 10′, an article 10 on which a film is deposited, amicrowave entrance window 15, a gas system 6 and 7, a water coolingsystem 18 and 18′, a halogen lamp 20, a reflector 21, and a heatingspace 3.

[0026] The article 10 to which a film is deposited is first set on thesubstrate holder 10′, and provided in a plasma generating space 1through the gate valve 16. The substrate holder 10′ is made of quartzlest it should disturb the microwave and the magnetic field. The wholeapparatus is evacuated to a vacuum of 1×10⁻⁶ Torr or higher using theturbo molecular pump 8 and a rotary pump 14. A gas which does notparticipate in the reaction (i.e., a gas which does not produce a solidupon decomposition reaction) such as hydrogen is introduced into theplasma generating space 1 through the gas system 6 at a flow rate of 30SCCM to adjust the pressure thereof to 1×10⁻⁴ Torr. Then, microwave of2.45 GHz is applied externally at a pulse period of 8 ms. The magneticfield is applied at about 2 KGauss using the Helmholtz coils 5 and 5′ tothereby generate a high density plasma in the plasma generating space 1.The gas is flown downward from the upper side of FIG. 1, however, it maybe flown upward from the lower portion of FIG. 1, or may be flown fromthe right to the left, or vice versa.

[0027] The gas which does not participate in the reaction or electronshaving a high energy discharged from the high density plasma reach andclean the surface of the article 10 on the substrate holder 10′. Then,while continuously introducing the gas which does not participate in thereaction, a reacting material (which forms a solid upon decompositionand reaction) in the form of a gas, liquid, or solid, such as ahydrocarbon gas [e.g., acetylene (C₂H₂), ethylene (C₂H₄), and methane(CH₄)], a liquid carbon compound [e.g., ethanol (C₂H₅OH) and methanol(CH₃OH)], and a solid hydrocarbon [e.g., adamantane (C₁₀H₁₆) andnaphthalene (C₁₀H₈)] is introduced at a flow rate of 20 SCCM. Thereacting material is converted into a plasma by virtue of the energiessupplied thereto. The pressure inside the vessel is adjusted to therange of from 0.03 to 30 Torr, preferably in the range of from 0.1 to 3Torr, specifically 0.5 Torr, for example, while maintaining the plasmaalready generated inside the vessel. The product gas can be concentratedper unit volume by thus elevating the pressure of the vessel, and itresults in increasing the rate of film growth. A gas can reach anywhereon an irregular surface of an article by elevation of the pressureinside the vessel.

[0028] Thus, the thin film material is deposited in a process whichcomprises once generating a plasma under a low pressure, increasing theconcentration of the active species of the reacting gas whilemaintaining the plasma state, forming active species excited to a highenergy state, and depositing the active species on the article 10provided on the substrate holder 10′.

[0029] The magnetic field as shown in FIG. 1 is generated by a Helmholtzcoil system using two ring-shaped coils 5 and 5′. A quarter of theelectric field and that of the magnetic field are shown in FIGS. 2(A)and 2(B). Referring to FIG. 2(A), the abscissa (X-axis) represents thehorizontal direction (the direction in which the reactive gas isdischarged) of the space 30, and the ordinate (R-axis) represents thedirection along the diameter of the Helmholtz coil. The curves drawn inFIG. 2(A) represent the equipotential plane of the magnetic field. Thenumerals placed on the curves indicate the intensity of the magneticfield obtained when the magnetic intensity of the Helmholtz coil 5 isabout 2000 Gauss. The magnetic field intensity over a largefilm-deposition area of the substrate in a region 100 in which theinteraction between the electric field and the magnetic field occurs canbe controlled to a nearly constant value (875 Gauss+185 Gauss) byadjusting the strength of the magnet 5, that is by adjusting currentflowing the Helmholtz coil 5. FIG. 2(A) shows the equipotential planesin a magnetic field; in particular, curve 26 is the equipotential planein the magnetic field for 875 Gauss, which corresponds to the ECRcondition.

[0030] The region 100 in which the resonance condition is satisfiedcorresponds to the area having a maximum electric field intensity, asshown in FIG. 2(B). In FIG. 2(B), the abscissa corresponds to the flowdirection of the reactive gas as in FIG. 2(A), and the ordinaterepresents the intensity of the electric field (electric fieldstrength).

[0031] It can be seen that the electric field region 100′ also yields amaximum intensity as well as the region 100. However, with reference tothe magnetic field (FIG. 2(A)), it can be seen that equipotential planesin the magnetic field are densely distributed in this region 100′. Itcan be understood therefrom that a film deposited on the substrate inthis region 100′ may have great variation in thickness along thediameter direction (the direction along the ordinate in FIG. 2(A)), andthat a favorable film is only obtainable in the region satisfying theECR condition, i.e., along 26′. In conclusion, no uniform andhomogeneous film can be expected in the region 100′. Film formation onan article may be carried out in the region 100′ in the case where afilm having a doughnut shape is formed.

[0032] A region in which the magnetic field maintains a constant valueover a large area and in which the electric field strength attains amaximum also exists at a symmetrical position of the region 100 withrespect to the origin. It is certainly effective to carry out filmdeposition at such a region so long as there is no necessity of heatingthe substrate. It is difficult to obtain, however, a means to heat thesubstrate without disturbance of the electric field generated by themicrowave.

[0033] Upon considering the ease of mounting and demounting of thesubstrate as well as the heating thereof, and the achievement of auniform and homogeneous film in view of the applicability of the processto the industrial mass production the region 100 as shown in FIG. 2(A)outstands as a position superior to other two regions.

[0034] As a consequence of the considerations set forth above, it wasmade possible in this embodiment of the present invention to form auniform and homogeneous film up to a 100-mm radius, more favorably, upto a 50-mm radius if a circular substrate 10 is placed in the region100. To obtain a film having the same uniform thickness as that of thefilm mentioned above but with a further larger area, e.g., a film havingan area 4 times as large as the film above, the frequency may be reducedto 1.225 GHz from the present 2.45 GHZ to thereby double the diameter(the direction along the R axis of FIG. 2(A)) of the deposition space.

[0035] A specific embodiment of a process using the complex pulse asshown in FIG. 3(A) can be exemplified by the deposition of a DLC film.It is known that the favorable bonding in a DLC film is in the form ofsp³ hybridization, and the point persists on how to reduce the sp²hybridization which is formed simultaneously with the sp³ hybridizationduring the film deposition process. Since the ratio of the dissociationenergy for sp³ hybridization to that for sp² hybridization isapproximately 6:5, the number of sp³ hybridization can be certainlyincreased by setting the energy of the first peak in the range of from 5to 50 KW, and that of the second peak to about ⅚ of the first peak,i.e., in the range of from 4.1 to 46 KW. The cross section of the thinfilm was examined with a scanning electron microscope to observe diamondcrystals. As a result, it was confirmed that diamond crystals grew intogranules. Particularly, the size of the diamond crystals was from 5 to10 times as large as that of the diamond crystals deposited by applyinga conventional stationary (continuous) microwave. Furthermore, it wascustomary in the conventional diamond films that they deposit initiallyas crystals of small diameter and gradually grow into crystals of largerdiameter, and that they thereby suffer poor adhesion with thesubstrates. In the diamond crystals deposited by the pulsed wave processaccording to the present invention, however, the diamond crystals werelarge even at the interface with the depositing surface. Thus, a filmcan be formed on the substrate with the superior adhesion therebetweenby the process according to the present invention. The electron beamdiffraction image of the film revealed spots ascribed to single crystaldiamonds, and it can be seen therefrom that a diamond structure clearlydevelop in the film by applying a power at an average output of 1.5 KWor higher.

[0036] Processes which utilize the complex waves obtained from a pulsedwave and a stationary continuous wave as shown in FIGS. 3(B) and 3(C)can be applied widely. In the case where waves of the same wavelengthare combined as is shown in FIG. 3(B), such as the combination of amicrowave with another microwave or that of a high frequency wave andanother high frequency wave, a uniform film can be deposited at a smallenergy consumption. If waves of differed wavelengths are combined asshown in FIG. 3(C), a film having excellent uniformity and adhesion canbe obtained, as exemplified by the case in which a pulsed microwave wasadded to a stationary continuous high frequency wave. Variouscombinations of the waves, for example, a complex of a pulsed DC with astationary continuous microwave, can be designed depending on theintended purpose. According to an embodiment according to the presentinvention, a polycrystalline film of silicon carbide can be deposited onthe substrate by using a gas of carbosilicide (methylsilane). It is alsopossible to deposit a boron nitride film by the process according to thepresent invention, by simultaneously flowing a boride (e.g., diborane)and a nitride (e.g., nitrogen) to effect the reaction therebetween.Furthermore, the process may be utilized for depositing thin films ofoxide superconductors such as Bi(bismuth)-based oxide superconductors,YBCO-type superconductors, Tl(thallium)-based oxide superconductors, andV(vanadium)-based (non-copper type) oxide superconductors. Similarly,thin films of aluminum nitride, aluminum oxide, zirconia, and boronphosphide can be deposited. Multilayered films thereof with diamond canbe produced as well. It is also an embodiment of the present inventionto deposit on an article, films of a metal having a high melting point,such as tungsten, titanium, and molybdenum or films of metal silicidesuch as tungsten silicide, titanium silicide, and molybdenum silicide;the metal film may be deposited by subjecting a halide or a hydride ofthe metal itself to a decomposition reaction on the article, and themetal silicide film may be deposited by reacting the halide or thehydride of the metal with silane.

EXAMPLE 2

[0037] A DLC film was deposited in the same manner as in Example 1,except for using a microwave complex pulsed waveform power as shown inFIG. 4 in place of the complex pulsed waveform power shown in FIG. 3(A).A pulsed 2.45 GHz microwave power having a two-step peak composed of afirst peak 30 of 50 KW and a second peak 31 of 46 KW, with a pulseperiod of 8 ms was externally applied.

[0038] The electron beam diffraction image of the film was completelyfree from halo patterns ascribed to amorphous substances, and itrevealed the film to be composed of diamonds having high crystallinity.The cross section of the thin film was examined with a scanning electronmicroscope to observe diamond crystals. As a result, it was confirmedthat diamond crystals grew into columnar crystals. Particularly, thesize of the diamond crystals was from 5 to 10 times as large as that ofthe diamond crystals deposited by applying a conventional stationary(continuous) microwave. Furthermore, it was customary in theconventional diamond films that they deposit initially as crystals ofsmall diameter and gradually grow into crystals of larger diameter, andthat they thereby have poor adhesion with the substrates. In the diamondcrystals deposited by the pulsed wave process according to the presentinvention, however, the diamond crystals were large even at theinterface with the depositing surface. Thus, a film can be formed on thesubstrate with the superior adhesion therebetween by the processaccording to the present invention. The electron beam diffraction imageof the film revealed spots ascribed to single crystal diamonds, and itcan be seen therefrom that a diamond structure clearly develop in thefilm by applying a power at an average output of 1.5 KW or higher.

[0039] The conventional diamond film deposition process using astationary wave could only provide a 10μ thick diamond film which easilyundergo peeling by simply rubbing the surface with bare hands. However,the pulsed wave process according to the present invention providesdiamond films of the same thickness as the conventional ones but whichare completely resistant against peeling even when they are rubbed witha sand paper. That is, the pulsed wave process according to the presentinvention is capable of depositing thin films of diamond havingexcellent adhesion with the substrate.

EXAMPLE 3

[0040] A DLC film was deposited by applying a microwave electric powerhaving a pulsed waveform as shown in FIG. 6(A) synchronously with theelectric power applied to generate a magnetic field having a pulsedwaveform as shown in FIG. 6(A). A pulsed 2.45 GHz microwave having apeak value of 5 KW was externally applied at a pulse period of 8 ms. Themagnetic field was similarly applied in pulses having a peak value ofabout 2 KGauss and at a pulse period of 8 ms, by operating the Helmholtzcoils 5 and 5′. The pulsed microwave and the magnetic field werecompletely synchronized to thereby provide a high density plasma in theplasma generating space 1.

[0041] In the embodiment, a thin film diamond was synthesized using ahydrogen diluted methanol as the starting material, applying a microwavepower at an average output of 1.5 KW (peak value: 3.4 KW) and a pulseperiod of 8 ms. The cross section of the thin film was examined with ascanning electron microscope to observe diamond crystals. As a result,it was confirmed that diamond crystals grew into granular crystals.Particularly, the size of the diamond crystals was from 5 to 10 times aslarge as that of the diamond crystals deposited by applying aconventional stationary (continuous) microwave. Furthermore, it wascustomary in the conventional diamond films that they deposit initiallyas crystals of small diameter and gradually grow into crystals of largerdiameter, and that they thereby suffer poor adhesion with thesubstrates. In the diamond crystals deposited by the pulsed wave processaccording to the present invention, however, the diamond crystals werelarge even at the interface with the depositing surface. Thus, a filmcan be formed on the substrate with the superior adhesion therebetweenby the process according to the present invention. The electron beamdiffraction image of the film revealed spots ascribed to single crystaldiamonds, and it can be seen therefrom that a diamond structure clearlydevelop in the film by applying a power at an average output of 1.5 KWor higher.

[0042] The experimentally developed process according to the presentinvention enables deposition of a partially crystallized thin filmsunder a wider range of film deposition conditions. Furthermore, thepulsed wave process according to the present invention enablesdeposition of uniform films on articles having irregularities on thedepositing surface, at a reduced energy consumption as compared with theconventional process using a stationary continuous waves.

[0043] While the invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

What is claimed is:
 1. A method for forming a film, said methodcomprising the steps of: introducing a reactive gas into a reactionchamber; supplying a pulsed electromagnetic energy having a highfrequency to said reactive gas sufficient to convert said reactive gasinto a plasma; and forming the film on a surface of an object, wherein aphoto energy is applied to said reactive gas during said pulsedelectromagnetic energy to maintain an activated state of said plasma.